116 HOW WE USE HEAT 



cooked in such vessels. Pressure cookers are commonly 

 used in high altitudes, but are also used advantageously 

 at low levels chiefly to save time in cooking, to save fuel, 

 and to make tough cuts of meat more tender. 



SELF-TESTING EXERCISE 



Select from the following list those words which best Jill the blank spaces 

 in the sentences below and arrange the words in proper numerical order. 

 A word may be used more than once. 



matter state heat hot 



cold temperature under thermometer 



pushes particle increases contract 



larger weight decreases change 



conduction force expand substance 



more conductors radiation reduction 



Gravity pulls on one cubic inch of cold water with (1) force 



than it does on one cubic inch of (2) water. As a result, the 



(3) water flows in (4) the (5) water and (6) it 



upward. Heat is transferred from particle to (7) in (&) 



by a process called (9) Metals are better (10) of heat 



than clothing. (11) is not always required to carry heat; 



in the transfer by (12) heat can pass through empty space. 



When most substances are heated, they become (13) or wo 



say they (14) The measurement of (15) by means of a 



(16) takes advantage of the (17) in size of bodies when 



heated to a higher temperature and of its (18) in size when 



it is cooled. Many substances like ice and lead, when heated, may 

 (19) their (20) and become liquids. 



STORY TEST 



FRED Is AT THE MICROPHONE TODAY TELLING 

 "WHAT HEAT CAN Do" 



Read carefully and critically. List all the errors and suggest correc- 

 tions. 



Fellow science students : From my study of heat I have come to 

 the conclusion that heat is a sort of circus trickster. He can get 

 aboard the molecules of air coming from the throat of a trumpeting 



